Hitch bar adapter



FIG. 1 is a side elevation view of a hitch bar adapter showing my new design;

FIG. 2 is a top plan view thereof; and,

FIG. 3 is a rear elevation view thereof.

The broken line showing portions of the hitch bar adapter is for illustrative purposes only and forms no part of the claimed design. 

I claim the ornamental design for an hitch bar adapter, as shown and described. 